How did some americans justify the spanish american war?

  Glad to see you are honest and admit that you really aren't looking for view points that disagree with you; not being sarcastic honestly enjoy the honesty. 
I do happen to think that the reason we went to war with Spain being the sinking of the Maine was probably false; most evidence now points to it being an accident aboard the ship but it was the emotional reason for the war. From that point it was not really justified. The real reason for that war was a desire to free this hemisphere from Spanish influence, minimize the slave trade still in those waters, increase American territory and get overseas basis for the U.S. military. Emotional reasons often hide the real reason for a war and it is true about the U.S. Civil War (wasn't about slavery really but about the power balance between the states nd federal government) and U.S. entry into World War 1 could not be justified by the sinking of the Lusitania as it was carrying war goods and ammunition which made it a legal target under international rules of war. So the reason for going to war did not justify actually doing it but the underlying reason would justify it from the aspect of the nation(s) going to war.

Ais your correct answer